Gene: [12q241/PAH] phenylalanine hydroxylase; phenylketonuria (phenylalanine hydroxylase deficiency);

GEN

The gene length is 96 kb. Exons: 13; introns: 12. The mature transcript is 2.4 kb in length. Phenylalanine hydroxylase is a homodimer with the MM of subunit 51.672 kD (451 amino acids)."

FUN

[1] Phenylalanine hydroxylase system includes three major components: phenylalanine hydroxylase itself (PAH); dihydropteridine reductase (GEM:04p153/QDPR), and tetrahydrobiopterin (BH4, cofactor).
[2] PAH is an iron-containing tissue-specific liver enzyme catalyzing the linked oxidation reactions: Phe --> Tyr and BH4 --> quinoid form of dihydrobiopterin; the latter is reduced into tetrahydro-BH4 by the correspondent reductase (QDPR) in the presence of NADH.
[3] BH4 synthesis includes four stages: (1) GTP-cyclohydrolase: GTP --> dihydroneopterin triphosphate (NPTP); (2) 6-pyruvoyltetrahydropterin synthase ((PVHPS): NPTP --> 6-pyruvoyltetrahydropterin; (3) and (4) are under investigation now, sepiapterin reductase is involved in reactions."

FAG

Aromatic amino acid (Tyr, Trp, Phe) hydroxylase genes are components of a multigene family and are located in similar chromosomes, 12q (this gene) and 11p (GEM:11p155/TH; GEM:11p1/TRPH)."

FOG

Mode of inheritance is autosomal recessive.

HET

[1] The loss of function of each of three PAH system components leads to progressive mental retardation early in life, along with development of neurological symptoms. "Classic" (severe) phenylketonuria is linked to PAH deficiency and atypical forms of phenylketonuria (hyperphenylalanemias) are linked to QDPR or BH4 deficiencies. The latter case has at least two forms, associated with genetic disruptions of the 1st and 2nd stages of BH4 biosynthesis - GTPCH and PVHPS deficiencies.
[2] "Classic" phenylketonuria was described by A.Folling in 1934. Atypical phenylketonurias (GTPCH and PVHPS deficiencies) were described by S.Kaufman in 1975-78 and in some other sources."

PRO

Probe PDL32B identigies PAH-linked RFLP D12S7.

POL

RFLPs for 8 restriction enzymes are revealed (sample of 132 chromosomes, Danish origin). Three RFLPs are located within 22 kb region at 5'-end of the gene: BGLII (+ allele=1.7 kb, frequency 0.226), PVUII/a (+/6.0/0.774), PVUII/b (+/9.1/0.105) - and five more within 31 kb region at 3'-end of the gene: ECORI (+/11.0/0.606), MSPI (+/19.0/0.545), XMNI (+/6.5/0.455), HINDIII (+/4.0/0.363), ECORV (+/25.0/0.499). The intervening 43 kb between these two clusters do not contain any RFLP. HindIII RFLP is due to 200 bp insertion/deletion (with GC sticky ends). Two haplotypes, the 2nd (-+--+-++, according to the above RFLPs) and the 3d (-+-+-+--) associate with PAH phenylketonuria in 58% (20+38) cases, which is seven times more often than with normal allele (8% = 5+3). A mutant allele was found with the aid of the 3d haplotype. This allele has G->A transition in 5'-donor splice site (GT) of intron 12, that leads to deletion of exon 12 along with introns 11 and 12 during mRNA splicing."

EAG

Human PAH forms syntenic group (chr 12) with PEPB (q21) and INFG (q24.1). Murine PEPB and INFG are also syntenic (Chr 10). Hybridization on chromosomes indeed localized murine PAH gene to 10C2-D1. The homology of these syntenic groups means that human and mouse ancestors diverged about 750 Myr ago."

REF

POL "Chakraborty &: Hum Genet, 76, 40-46, 1987
PND "Daiger SP &: Lancet, 1, 229-231, 1986
MUT "DiLella AG &: Nature, 327, 333-336, 1987
MUT "DiLella AG &: Nature, 322, 799-803, 1986
MEB "Kaufman: Enzyme, 38, 286-295, 1987
CLO,SEQ "Kwok SC &: Biochemistry, 24, 556-561, 1985
EVO "Ledley FD &: CCG, 47, 125-126, 1988
POL "Lidsky AS &: AJHG, 37, 619-634, 1985a
PND "Lidsky AS &: Lancet, 1, 549-551, 1985b
LOC "Lidsky AS &: PNAS, 82, N18, 6221-6225, 1985c
LOC "Lidsky AS &: AJHG, 36, 527-533, 1984
MUT "Marvit &: NAR, 15, 5613-5628, 1987
PRO "O'Connell P &: Genomics, 1, 93-102, 1987
PRO,MUT,POL,GEN,POG "Okano Y &: Genomics, 9, N1, 96-103, 1991
MUT,POG "Wang &: Somat Cell Mol Genet, 16, 85-89, 1990
MUT,POL,POG "Woo SLC: Biochemistry, 28, N1, 1-7, 1989
POL "Woo SLC: AJHG, 43, 781-783, 1988
CLO,PND,MGC "Woo SLC &: Nature, 306, 151-156, 1983

SWI

SWISSPROT: P00439

KEY

neu, mtbd

CLA

coding, basic

LOC

12 q24.1

MIM

MIM: 261600

EZN

ENZYME: 1.14.16.1

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